The CSS `calc()` property facilitates straightforward arithmetic computations within your stylesheets. Below is a rule set showcasing the application of CSS `calc()`:
As illustrated in the example above, the CSS `calc()` property enables dynamic computation of the result from subtracting two CSS length values directly within your stylesheet, without the need for JavaScript, even when the length values are in different units.
Arithmetic operations that can be performed with CSS `calc()` include:
– Addition
– Subtraction
– Multiplication
– Division
CSS `calc()` operates on a variety of numerical CSS values, such as:
– Length
– Time
– Angle
– Frequency
– Unitless integers and numbers
CSS `calc()` cannot handle CSS color values or other CSS data types.
The practicality of CSS `calc()` becomes evident when performing mathematical calculations on numerical values with different CSS units, especially when dealing with a blend of relative and fixed units.
An instance where the `calc()` property should not be used is demonstrated below:
In the style rule provided, the calculation can be easily done manually. For enhanced CSS readability and to prevent unnecessary browser computations that may slow down web pages, it is advisable to use a physical calculator for the arithmetic:
The `calc()` property is particularly beneficial when one unit is relative and the other is fixed, a feature that is particularly advantageous in responsive web design. For example, a centered container can maintain 20px margins on its left and right sides, irrespective of the screen size:
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This example of CSS `calc()` accounts for a vertical scrollbar and ensures content readability across devices, requiring minimal CSS and HTML. Other responsive design techniques for achieving a similar result might involve more code, including negative margins, media queries, and unnecessary HTML nesting.
The specifications for CSS `calc()` are outlined in the W3C CSS Values and Units Module 3, which is currently at the Candidate Recommendation (CR) stage, two levels from finalization.
It is important to note that CSS `calc()` is one of the three CSS features in the module’s specifications that may be dropped, as stated in the CR:
> “The following features are at-risk and may be dropped during the CR period: ‘calc()’, ‘toggle()’, ‘attr()’.”
As of now, CSS `calc()` is supported in approximately 82% of web browsers, as per caniuse.com data. Internet Explorer 9 has partial support, while subsequent versions offer full feature support.
